JPH02222240A - Transmission method for hierarchical system - Google Patents

Abstract

PURPOSE:To enhance the convergence of outgoing data and to built up the system with low cost by adopting the broadcast system for outgoing transmission and adopting the polling response system for incoming transmission so as to send data. CONSTITUTION:A slave station address in common is set to all slave stations S1-SN, which are in standby in the reception mode and when a broadcast frame 102 is received from a master station M, a slave station address specific to each station is set and they are in standby in the transmission mode. When a polling frame from the master station M is received by each wave station, the slave stations S1-SN reply response frames 104, 106 and 108 to the master station M, and in standby in the reception mode while the common slave station address is set again. Thus, the convergence of outgoing data (arrival of data with less time difference to each slave station) sent from the master station to the slave stations S1-SN is enhanced and the system is built up with low cost.

Description

[Detailed description of the invention] [°Industrial application field]

The present invention relates to communication between a master station and slave stations in a hierarchical system in which a master station as a higher-level computer and slave stations as multiple lower-level computers (or control devices) are connected to a common transmission path. It relates to a method (transmission method), in particular, it improves the flux of the downlink data transmitted from the master station to the slave stations (i.e., data arrives at each slave station with little time difference), and it is possible to construct a system at a low cost. The present invention relates to a hierarchical system transmission method. Note that in the following figures, the same reference numerals indicate the same or corresponding parts.

[Conventional technology]

Figures 3 and 4 are explanatory diagrams of conventional transmission methods between multiple stations connected to a common transmission path. Figure 3 is an illustration of the broadcast method, and Figure 4 is an explanatory diagram of the selecting response method. be. In FIG. 3, stations (1), (2), and (3) are stations STI, ST2, and ST2, respectively, as equal stations. STN
This is a time chart (sequence) of communication. In this broadcast transmission system, each of the N stations can have the right to transmit to other stations like a master station, so each station is called a station for convenience. In addition, in the communication sequences in the following figures, including this figure, the upper side of the baseline indicates the timing of transmission by the station (or station) in question, and the lower side of the baseline indicates the timing of reception by the station (or station) in question. shall be taken as a thing. To explain FIG. 3, station STI, which is an initial master station, transmits a broadcast frame 501 consisting of a signal indicating that a broadcast is to be performed and transmission data addressed to each station arranged in a predetermined order. The broadcast frame 501 is transmitted to each other station ST2.
~ Received by STN. When station STI transmits broadcast frame 501, it simultaneously passes a token (transmission right) to station ST2. Station ST2, which received the token, then becomes the master station and transmits the broadcast frame 502 and station ST3.
Send a token to . In this way, the master station moves in order and data transmission is performed. Note that this token movement method is called a token pass method. The advantage of this broadcast transmission system is that data can reach each station simultaneously. Next, in FIG. 4, (1), (2), and (3) show the communication sequences of master station M, slave station SL, and slave station SN, respectively. In this selecting response transmission method, master station M Slave station 5l-3
By sequentially specifying N, communication is performed between the slave station and the master station each time N is specified. That is, in FIG. 4, the master station M sends a selecting message to the slave station S1, which consists of an address specifying this station S1, a command to perform transmission using the selecting response method, and transmission data for this station 31. frame 601
Send. Slave station S1, which has received selecting frame 601, transmits to master station M a response frame 602 consisting of a signal indicating that a reply is to be made and data to be sent to the master station. Next, the master station M transmits a selecting frame 603 similar to the above to the slave station S2,
A response frame 604 is received from slave station S2. In this way, the master station M sequentially sends the selecting frame to the slave stations and performs data transmission. The advantage of this selecting response transmission method is that the hardware and software of the slave station is relatively simple.

[Problem to be solved by the invention]

However, the broadcast transmission method mentioned above has
There are the following problems. That is, since all stations can act as master stations, the hardware becomes complicated and costly, and each station must perform processing such as token movement, which increases the burden on the software. On the other hand, the aforementioned selecting response transmission method also has the following problems. That is, the hardware and software of the slave stations are relatively simple, but data cannot reach each slave station at the same time. Generally, when passing commands from a higher-level computer (master station) to a lower-level computer (slave station), data flux characteristics are important, especially when the lower-level computer is a control device, but as mentioned above, in the broadcast transmission method, data flux characteristics This is good, but the cost of the transmission equipment increases.1. The burden on the software will also increase. On the other hand, selecting
Although the response transmission method reduces system cost, it does not maintain data flux. Therefore, the present invention provides a transmission method for a hierarchical system in which particularly important downlink data (commands to a control device) is transmitted using a broadcast method, and uplink data that does not particularly require flux characteristics is communicated using a polling response method. The object of the present invention is to solve the above problem.

[Means to solve the problem]

In order to solve the above-mentioned problems, the method of the present invention provides a method for transmitting a hierarchical system in which a master station (such as M) and a plurality of slave stations (such as SL to SN) communicate with each other via a common transmission path. In the method, the master station simultaneously transmits the data addressed to each of the slave stations in a predetermined order to all the slave stations simultaneously (by using a polling response transmission method), and (by using a polling response transmission method) One by one, each slave station is specified one by one, and the data of that station is received from the slave station.Transmission method.

[For use]

All slave stations initially set a common slave station address and wait in reception mode. When the slave station receives a broadcast frame from the upper station, it sets a slave station address unique to each station and waits in transmission mode. When each slave station receives an inter-station polling frame from the upper station, each slave station returns a response frame to the upper station, sets the common slave station address again, and repeats the operation of waiting in reception mode.

【Example】

Next, the present invention will be explained in detail based on FIGS. 1 and 2. FIG. 1 is an explanatory diagram of a transmission method as an embodiment of the present invention, and (1), (2), and (3) in the figure show communication sequences of master station M, slave station St, and slave station SN, respectively. , (4) and (5) in the same figure are respectively slave stations 51. It shows the time transition of SN transmission and reception modes. To explain Fig. 1, the host computer which is the master station M initially sets the initial frame 10 for all seven slave stations.
1 to perform initialization such as specifying the slave station connected to the transmission path. As a result, all slave stations 31 to SN enter the reception mode and wait at the slave station address "0" (period TI). Next, the master station M transmits a broadcast frame 102 specifying the slave station with address "0". Note that this broadcast frame 102 has a predetermined length of each slave station Sl to SN.
The data for each is arranged in order. Therefore, each slave station 31 to SN can read data destined for itself from this broadcast frame 102. Each slave station 5l-3N that has successfully received the broadcast frame 102 in this way enters the reception mode and waits at the slave station address unique to each station (period T2
). Next, the master station M transmits a polling frame 103 intended for the slave station S1, and requests transmission to the slave station S1. Slave station S1 that received polling frame 103 transmits response frame 104 to master station M,
Switch to reception mode again (period T3). The master station M performs the same thing in order for the slave stations 82 to SN. When this communication up to the slave station SN is completed in this way, the master station M again uses the broadcast frame 10.
Send 2. In this way, transmission operations are repeatedly performed using the broadcast method for downlink transmission and the polling and response method for uplink transmission. FIG. 2 shows the flow of data between master station M and slave stations 5l-3N in the transmission shown in FIG. That is, the broadcast frame 102 from the master station
1-3N is reached. However, slave stations Sl, S2.
SN response frame 104.106.108
reaches only master station M.

【Effect of the invention】

According to the present invention, in a hierarchical system in which a higher-level computer and a plurality of lower-level computers (control devices) communicate with each other via a common transmission path, a broadcast method is used for downlink transmission, and a polling response method is used for uplink transmission. Since data transmission is carried out using the above-described method, it is possible to improve the flux of downlink data and to construct a system at low cost. Note that this flux property is effective, for example, when a host computer gives a speed command to a control device for a plurality of motors in a process line for steel or the like.

[Brief explanation of the drawing]

Figure 1 is a time chart showing the transmission method as an embodiment of the present invention, Figure 2 is a diagram showing the flow of transmission data in the present invention, Figure 3 is an explanatory diagram of the broadcast transmission method, and Figure 4 is the selection diagram. FIG. 2 is an explanatory diagram of a response transmission method. M: Master station, 5l-8N Nislep station, 101: Initial frame, 102 Nibroadcast frame, 103 Polling frame for Nislep station Sl,
104 Response frame from Nisrep station S1, 1
05 For Nislepe station S2, polling frame, 106
:Response frame from slave station S2, 107:
Polling frame for slave station SN, 108 Figure 2 of response from Nislep station SN

Claims (1)

[Claims] 1) A transmission method for a hierarchical system in which a master station and a plurality of slave stations communicate with each other via a common transmission path, wherein the master station transmits data addressed to each of the slave stations. is simultaneously transmitted to all slave stations in a predetermined order, and each slave station is designated one by one in order to receive the data from that slave station. A transmission method for a hierarchical system.